Pathological femoral fracture due to rhabdomyosarcoma in a cat.

An eight-year-old neutered male domestic shorthaired cat was presented with non-weightbearing lameness of the right hindlimb. On radiography, a pathological, metaphyseal femoral fracture was apparent, with areas of bony lysis directly surrounding the fracture site. The cat underwent amputation of the limb. Histopathological examination revealed the presence of a tumour of mesenchymal cells with cytoplasm-containing vacuoles which stained positive with the periodic acid-schiff reaction, indicative of glycogen granules that may be found in rhabdomyosarcoma cells. In addition, the tumour cells stained positive for vimentin and desmin on immunohistochemical examination, thus confirming the diagnosis of rhabdomyosarcoma. In spite of the radical surgery performed, the cat was euthanased due to a recurrence at the amputation site four and a half months later.